In recent years, an IC having a function of wirelessly transmitting data such as a wireless tag, an IC tag, or a noncontact IC card has been actively developed. Both of the IC tag and the noncontact IC card require an antenna for transmitting data wirelessly.
There is a built-in antenna in which an antenna is formed directly on an IC chip, and an external antenna in which an antenna is formed over a base material different from an IC chip. An external antenna coil is the mainstream of an antenna since it can extend communication distance due to its large antenna.
As a method for manufacturing an external antenna, a method employing etching, a printing method, or the like is known. In the case of etching, metallic foil such as copper or aluminum formed over a plastic substrate by vapor deposition or pasting is formed into a desired shape by a photolithography process and an etching process. In the case of printing, conductive polymer is printed on a film-like base material into the shape of an antenna coil by technique such as a screen printing method.